1. Field of the Invention
The present invention relates to mechanical rotary seals.
II. Description of the Related Art
Compact self-contained cartridge type mechanical seals, such as the ones shown in FIGS. 1 and 2, are specifically designed for high quantity production of industrial and domestic pumps handling water, steam, oil, hydraulic fluids, refrigerants, and gases at pressures as high as 100 psi. The seal shown in FIG. 1 is known in the industry as a shaft mounted seal and presses onto the shaft of a pump, while the seal in FIG. 2 is known as a bore mounted seal and presses into the pump housing. Such seals use coil springs 10a and 10b, respectively, to maintain an axial force between face seal ring 12a and complementary surface 14a in FIG. 1, and face seal ring 12b and complementary surface 14b in FIG. 2. Sealing members 16a and 18a are used to seal the face members to the shaft and housing in FIG. 1. Sealing members 16b and 18b are used to seal the facing members to the housing and shaft in FIG. 2. In such arrangements, reinforcing members 20a, 22a and 24a are used to hold sealing member 16a in place in the arrangement shown in FIG. 1. Reinforcing members 20b, 22b and 24b are used to hold the sealing member 16b in place in FIG. 2.
There are many drawbacks to these coil spring seal designs. The large number of component parts makes manufacture complicated. The use of a steel spring coil produces an uneven load distribution on the periphery of the carbon face member. The seal is unsuitable for acids and highly corrosive fluids because it contains metallic parts. The seal in FIG. 2 has metal-to-metal interference with the pump housing which, when installed, requires the use of an "O" ring or a very tight fit using a mastic sealing material applied during the installation.
U.S. Pat. No. 3,185,488 discloses a mechanical rotary seal having a sealing member with reinforcing members which does not require the use of a coil spring to maintain the face members in positions against each other. Although several of the drawbacks of the coil spring biassed seal are overcome by this arrangement, other drawbacks remain and new problems are created. In particular, the built-in reinforcing members constitute an expensive construction. Also, the presence of such reinforcing members makes the seal difficult to install because it binds when it is assembled to the shaft or housing due to its requirement of being slid into position as a single unit so that a tight seal can be maintained. Furthermore, such seals have a very short operating range of axial compression which is unforgiving in low tolerance design and operating situations. In addition, the axial force over the operating range varies considerably.
Accordingly, it is an object of the present invention to provide a seal which does not have a large number of component parts which makes manufacture complicated.
It is another object of the present invention to provide a biassed member which provides an even load distribution on the periphery of the carbon face seal ring.
It is a further object of the present invention to provide a seal having no metallic parts, thereby making the seal suitable for use with acids and highly corrosive fluids.
It is also an object of the present invention to provide a seal having no metal-to-metal interference with the pump housing and no need for the use of an "0" ring or mastic sealing material.
It is an additional object of the present invention to provide a seal which requires no reinforcing members to hold the sealing members in place.
It is another object of the present invention to provide a seal which can be easily assembled and installed on the shaft and housing without binding the shaft and housing during assembly.
It is a further object of the present invention to provide a seal having a long operating range of axial compression.
It is also an object of the present invention to provide a seal having a substantially constant axial force over the operating range of axial compression.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.